def try_decide_less_weak(lhs, rhs):
"""Weak decision procedure returning True, False, or None."""
assert isinstance(lhs, Term), lhs
assert isinstance(rhs, Term), rhs
# Try simple cases.
if lhs is BOT or lhs is rhs or rhs is TOP:
return True
if lhs is TOP and rhs is BOT:
return False
# Destructure JOIN.
if is_join(lhs):
return trool_all(try_decide_less_weak(i, rhs) for i in iter_join(lhs))
if is_join(rhs):
# This requires we give up at unreduced terms.
return trool_any(try_decide_less_weak(lhs, i) for i in iter_join(rhs))
# Destructure ABS.
while is_abs(lhs) or is_abs(rhs):
lhs = unabstract(lhs)
rhs = unabstract(rhs)
assert lhs is not rhs, lhs
# Destructure APP.
lhs_head, lhs_args = unapply(lhs)
rhs_head, rhs_args = unapply(rhs)
# Try pointwise comparison.
if lhs_args and len(lhs_args) == len(rhs_args):
if try_decide_less_weak(lhs_head, rhs_head) is True:
if all(try_decide_less_weak(i, j) is True
for i, j in zip(lhs_args, rhs_args)):
return True
# Give up at unreduced terms.
if is_nvar(lhs_head) or is_nvar(rhs_head):
return None
if is_abs(lhs_head) or is_abs(rhs_head):
return None
if lhs_args and not is_ivar(lhs_head):
return None
if rhs_args and not is_ivar(rhs_head):
return None
# Distinguish solvable terms.
if is_ivar(lhs_head) and is_ivar(rhs_head):
if lhs_head is not rhs_head or len(lhs_args) != len(rhs_args):
return False
return trool_all(
try_decide_less_weak(i, j)
for i, j in zip(lhs_args, rhs_args)
)
# Distinguish quoted terms.
if is_quote(lhs_head) and is_quote(rhs_head):
return try_decide_equal(lhs_head[1], rhs_head[1])
# Anything else is incomparable.
return False
def test_trool_any(expected, values):
assert trool_any(values) is expected
